1. Field of the Invention
The present invention relates to cellular communication networks, and more specifically to cellular communication network which prioritize access to channel assignments.
2. Background and Objects of the Present Invention
The capacity of a wireless or cellular communication system and its ability to cope with a given traffic density are related in that a wireless or cellular (hereinafter "wireless") system must be able to accommodate the peak traffic density that is likely to be encountered. The inability of a wireless system to deal with maximum communication traffic is sometimes referred to as the "capacity limit". A capacity limit may be different for different portions of a cellular system depending on a variety of variables. There are, at present, three factors that limit the capacity provided by a wireless system and they are:
1. the total amount of spectrum available; PA1 2. the co-channel interference level that can be tolerated by the radio equipment for acceptable call quality; and PA1 3. the cell size, large or small, can be established.
The total amount of spectrum available can be limited by, among other things, governmental regulations and competing wireless devices and services. The use of digital wireless technology over analog wireless technology has decreased the spacing between channels and increased the number of channels available. Increasing system capacity by reducing the channel spacing lowers the protection against the co-channel interference and thereby necessitating a higher integer cell repeat pattern. The capacity gain achieved by a reduction of channel spacing is therefore offset by an increase in cluster size.
Decreasing cell size increases capacity of networks but adds expense and creates the problem of finding cell sites at precise locations in urban environments where site spacing is the closest an the cost is at a premium. Of course, site location inaccuracy inevitably leads to a dilution of the potential increase in capacity of a reduced cell size.
At subscriber demand increases, it continues to be necessary to explore additional methods of increasing capacity. One technique explored has been the use of overlaid cells, which allows the reuse of frequencies at each site. The overlaid cells operate provided that they are only used by mobile phones/devices within a smaller radius than that of the macrocell, thereby adding additional capacity at the center of the cell. The overlaid cells use frequency groups that are already allocated to normal adjacent macrocells. The reuse distance for the overlaid cell appropriate to a seven-cell cluster can thus be maintained, and hence the quality of service is approximately the same as that of the main cell plan.
Inevitably, there is a price to pay for such improvements; in the case of overlay cells, the system complexity is greatly increased. Software is required in the base station to recognize mobile phones that access the site with a strong signal level; these mobile phones can then be allocated to channels in the overlaid cell instead of the macrocell base on the assumption that they are close to the base station. The macrocells are reserved for weaker signals which probably originate from more distance mobile phones. Furthermore, the added problem of intracell handover is added making the system even more complex.
Economically speaking, there is a motivation to handle extremely high capacity situations that occur from time to time without requiring each cell to have the electronic connection capacity to handle a high/peak capacity when usually there is not a high/peak capacity situation. There is a need for a system that can handle an over capacity or high capacity situation which drops the least number of calls. There is a need for a wireless telecommunication system than can handle peak moments and decide how to prioritize calls when the communication traffic exceeds that of a cell's capacity.
What is needed is a system adapted to handle the growing use and demand of a cellular channels without degrading the system by adding too much complexity, and that can maintain customer satisfaction by not dropping a customer's call for seemingly no reason. Furthermore, such a technique for increasing the efficiency of a wireless system should further optimize virtually any wireless system (digital or analog) by utilizing reserved channels without disabling a priority user from utilizing such a reserved channel when necessary. What is also needed is a wireless system to prioritize calls when the available channels are being heavily utilized.